Acquisitions - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	9 Months Ended				9 Months Ended	6 Months Ended	9 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2013 gal sites	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Jun. 07, 2013	Dec. 31, 2012	Sep. 30, 2013 Natural Gas [Member]	Jun. 30, 2013 Eastern Shore Gas Company [Member] Customer	Sep. 30, 2013 Austin Cox [Member]	Jun. 30, 2013 Propane Acquisition [Member] Customer	Sep. 30, 2013 Propane Acquisition [Member]	Dec. 31, 2013 Propane Acquisition [Member]	Feb. 05, 2013 Propane Acquisition [Member]
Business Acquisition [Line Items]
Purchase Price Adjustment		$ 543,000
Transaction costs, tax	726,000
Number of residential and commercial customers receiving propane gas distribution service								11,000		3,000
Minimum number of customers to whom gas distribution systems and bulk delivery service provided								500
Purchase price allocated to property, plant and equipment	12,600,000				105,000								1,600,000
Purchase price allocated to propane and other inventory	344,000				94,000								502,000
Receivables	2,500,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	227,000
Number of leased propane tanks	13
Storage capacity of leased propane tanks	570,000
Duration of lease of propane tanks	6 years
Monthly fee payment in year one	42,000
Monthly fee payment, year two to six	125,000.00
Annual Estimate Of Volume Of Propane To Be Purchased	7,400,000
Number of years to purchase propane under contract	6 years
Capital Lease Obligations	7,100,000	7,042,000	7,042,000			0
Amortization expense		62,000	83,000
Capital lease asset	7,100,000
Amortization of leased asset		63,000	84,000
Purchase price allocated to intangible assets related to customer list					250,000								300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			5 years								12 years
Purchase price allocated to goodwill					173,000
Payments to Acquire Businesses, Gross			(19,367,000)	(124,000)			16,500,000		600,000			2,900,000
Sales Tax		726,000	726,000
Goodwill		$ 4,716,000	$ 4,716,000			$ 4,090,000							$ 453,000